Magnetic sensors such as Hall sensors and magnetoresistance sensors are widely used in daily life as speed sensors, position sensors in refrigerators, mobile phones, washing machines, and laptops, and the like.
Hall sensors where the Hall resistance changes under an external magnetic field typically make use of semiconductors such as Silicon, InAs, GaAs and InSb. Hall sensors based on Silicon are suitable for monolithic integration, but due to low mobility of the carriers, have a poor sensitivity which is defined as the voltage generated for unit magnetic field (mV/mT). Hall sensors based on InSb semiconductors have a high sensitivity due to the high mobility of about 40,000 cm2/(V·s), but this high mobility requires an expensive micro thick film. Also, these InSb based Hall sensors have an undesirable large change in resistance for unit degree of temperature change, i.e. a high temperature coefficient of resistance. Further, Hall sensors have relatively high sensitivity in moderate and high magnetic field; however, the sensitivity is poor in low fields.
Researches have been done on magnetoresistance sensors for the availability, the low energy consumption and the low cost. Magnetoresistance measures a change in the electrical resistance of a material under an external magnetic field. This important technological feature contributes to the success of the information storage industry in reading data from a magnetic hard disk media. A read head incorporated with the material having magnetoresistance is extremely sensitive to low (stray) magnetic field. Magnetoresistance sensors have a high sensitivity in low fields. However, they suffer from cross field error, especially anisotropic magnetoresistance sensor, and are not suitable for detecting large fields.
Thus, what is needed is a magnetic sensor having a high sensitivity in both low and high magnetic fields and a low temperature coefficient of resistance as well as low costs. Also, thin film based sensors are more preferred than bulk ones due to its compactness and cost effectiveness. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background of the disclosure.